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Raffinate Handling In Recip Comp Of Lub Refinery


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#1 Shashank Pathak

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Posted 24 November 2016 - 04:06 AM

Background of Operation: Single stage recip comp operating in Solvent extraction Unit. In Lub oil base stock production, different grades of distillates from vacuum distillation unit are routed to SEUs for Aromatics removal. The Raffinate from SEUs routed to LOUP for Hydro-desulphurization and Hydro-Denitrification followed by Isomerization reaction.
 
Details of Compressor: Single stage IR-ESH Model - NL-equipped with KO drum (with demister) at suction line. After start up, compressor runs through 2 weeks time and then sound starts building up for next 2/3 weeks time. With more adverse noise, compressor get stopped. Raffinate gets found inside compressor cylinder. This is recurring cycle of operation.
 
Details of Process:
Feed goes from hydrofiner reactor to high pressure separator. Then it is paased through hydrofined raffinate cooler. From cooler,it passes through recycle gas compressor KO drum before entering compressor suction volume bottle.
 
Raffinate is found inside compressor cylinder. It is kind of Wax slug (semi solid, I am not sure if this is technically correct terminology) which gets accumulate compressor cylinder over the period of 4/6 weeks. Compressor then need to stop.
 
MY Query - From some literature reference, it is found that, this is Lub base stock process in lub refinery wherin it is the step of subjecting sasid dewaxed oil to extraction with a solvent having selective affinity for Aromatic hydrocarbons so as to separate the feed into the raffinate portion and the extract portion, and removing the solvent from said extract portion to obtain an extract oil.
 
Is this common phenomenon happening with such recip compressor in this process? 
Any options for filteration or raffinate removal solutions?  
Thanks in advance, Kind RegardsShashank

#2 Bobby Strain

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Posted 24 November 2016 - 09:59 AM

A sketch would help. Showing operating conditions.

 

Bobby



#3 Shashank Pathak

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Posted 30 November 2016 - 04:58 AM

Thanks Bobby....

 

Sorry, i could not upload sketch here....struggled lot :)

 

Operating conditions at inlet to retreat gas compressor at compressor cylinder.....

 

1] Suction Pressure - 52 bar a, suction temperature - 55 deg c

2] Discharge pressure - 72 bar a, discharge temeprature - 95 deg c

3] Capacity at inlet - 841 kg/hr

 

Gas flow to compressor through following process flow

 

4] Feed stock operating pressure at Hydrofiner reactor -  66 bar a

5] Operating pressure at High Pressure separator - 64 bar a

6] Recycle gas cooler - 58.38 bar a

7] Recycle gas KO Drum - 57.5 bar a

8] Flow goes to compressor from KO drum.

 

Gas composition - Mol wt 6.3 g/mol

Hydrogen 85.96%, H2S - 10%, Methane - 2.55%, Propane - 0.74%, iso-butane-0.44 %, Ethane - 0.23%, iso-pentane & n-hexane - 0.04%,



#4 Bobby Strain

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Posted 30 November 2016 - 04:23 PM

I think that I would trace and insulate the piping from the drum to the compressor to prevent condensation. And be sure that you have a clean demister in the KO drum.

 

Bobby



#5 Shashank Pathak

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Posted 12 December 2016 - 12:59 AM

Thanks Bobby, let me see how this helps us.






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